Sonic boom

A sonic boom is made by the sudden release of pressure that is built up by the shock wave. The change in pressure is small—similar to the pressure change you feel when you descend a few floors in an elevator. But because the change happens very, very quickly, you hear a loud boom. Not all sonic booms reach the ground, but those that do arrive less than one minute after flyover and generally last less than one second.

As shock waves spread across the landscape, sonic booms are continuously created along the flight path. If you continued to move with the plane at the same supersonic speed, you'd hear continuous booms. Otherwise, you hear the boom created when the plane is overhead.

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